Legionella pneumophila is a valuable model organism for identifying bacterial determinants that modulate vesicular transport. Central to the process of L. pneumophila manipulation of host membrane trafficking is a type IV-related protein secretion system called Dot/lcm that is required for the establishment of a vacuole that supports bacterial replication in eukaryotic cells. The goal of this grant is to understand how the Dot/lcm system governs biogenesis of the specialized vacuole in which L. pneumophila replication occurs. We have identified and determined the biological activities for several L. pneumophila effector proteins translocated into host cells by the Dot/lcm system. Our goal over the next granting period will be to elucidate the molecular mechanisms that underlie the functioning of these Dot/lcm effectors to understand how they manipulate host proteins important for replication of L. pneumophila inside of eukaryotic cells. This work will provide a more detailed understanding of how Dot/lcm effector proteins modulate host cell interactions to facilitate the intracellular replication and pathogenesis of L. pneumophila.